The Beauty of a ThinkPad Nubbin Light Dimmer Switch

ThinkPad laptops (originally manufactured by IBM, but now by Lenovo) hold a special place of honor in the tech world. They’re famous for being rugged and reliable no-nonsense spreadsheet-crushing business machines. They’re also famous for what Guy Dupont calls “nubbins,” but which I know by a couple of other names that are too vulgar to print here. The nubbin is a small rubber mouse controller situated in the middle of the keyboard where no-nonsense spreadsheet-crushing business people can reach it easily. Dupont had the brilliant idea to turn a nubbin into a dimmer switch control for his dinner room lights.

“Nubbin” is not, of course, the technical term. Wikipedia calls it a “pointing stick,” which is ridiculous — it is clearly not a stick. IBM dubbed it the “TrackPoint” when they began slapping it on ThinkPad laptops in 1992. If you search “TrackPoint” on Amazon, eBay, or AliExpress, you’ll find several standalone modules and Dupont used one of those for this project.

The TrackPoint module Dupont purchased came pre-soldered on a USB controller board. That lets users plug the module directly into a computer and use it like a mouse. But Dupont didn’t want to connect his nubbin to a computer, he wanted to use it to adjust a dimmer switch. His first thought was to remove the USB controller board and connect the TrackPoint module to a microcontroller development board, but he ran into issues with communication.

The solution he eventually settled on is a bit messy, but it works. A Seeed Studio XIAO RP2040 development board acts as a USB host for the TrackPoint controller board. It reads the “mouse” movement and uses that to brighten or dim the lights through a mains dimmer module.

But there was still a problem: Internet of Things (IoT) control. Any light control made in 2024 needs internet connectivity and the XIAO RP2040 doesn’t have a Wi-Fi adapter. So Dupont added an Adafruit QT Py ESP32-S3 development board, purely to take advantage of the ESP32’s built-in Wi-Fi adapter. That let Dupont control the dimmer switch with the nubbin mounted on a plate on the wall and through his local Wi-Fi network. He even made a simple smartphone app that lets users adjust the dimmer by flicking a virtual onscreen nubbin.

I worked for Lenovo right after they took over the ThinkPad line and I’ve owned several ThinkPad laptops over years (and still use one). Naturally, I’m a big fan of ThinkPads, nubbins, and this project and I’m sure it will appeal to many of you, too.